Top portion of a spring core



FIG. 1 is a top plan view of a top portion of a spring core showing our design;

FIG. 2 is an enlarged fragmentary view taken from the bottom left corner in FIG. 1;

FIG. 3 is a side elevational view;

FIG. 4 is an enlarged fragmentary view taken from the far left in FIG. 3;

FIG. 5 is a side elevational view, showing the side opposite that shown in FIG. 3;

FIG. 6 is an enlarged fragmentary view taken from the far left in FIG. 5;

FIG. 7 is an end elevational view;

FIG. 8 is an enlarged fragmentary view taken from the far left in FIG. 7;

FIG. 9 is an end elevational view showing the end opposite that shown in FIG. 7; and,

FIG. 10 is an enlarged fragmentary view taken from the far right in FIG. 9.

The broken lines are for environmental purposes only and form no part of the claimed design. 

The ornamental design for a top portion of a spring core, as shown and described. 